Bulk particulate solids in the form of powders or granules are commonly loaded into large fabric bags and the loaded bags, expanded by the solids, are transported by truck or rail from a manufacturer to an end user. Typically, the bags are expanded on loading from the top, and a bottom spout is opened for discharge of the particulate solids while the bag is lifted and, often shaken, to aid the flow of particulate solids through the spout. Ideally, after discharge of the solids the bag is then reused in the same service.
The time required to unload these bags is typically slow, and often the solids cannot be discharged without ripping open the bags; because the particulate solids fail to flow through the spout. For example to unload 24 bags each of which contains one ton of adsorbent clay requires at least 4 hours, and often 6 hours. The bottom of some of the bags are often ripped open to remove the solids because solids flow from the bottom spout ceases, or cannot be initiated. The time required for emptying these bags burdens the process in which the particulate solids are used; and when a bag is ripped open it is destroyed. This is costly, particularly when the bag cannot thereafter be reused.
Some fabric bags in their design do not include a bottom spout, and these bags are always destroyed when they are ripped open to empty the bag of its contents. This type of bag is disclosed, e.g., in U.S. 4,307,764. Flexible bags provided with bottom spouts through which particulate solids can be removed via gas assist means are described e.g., by U.S. Pat. No. 2,829,803 and U.S. Pat. No. 4,167,235. In the former patent, a suction tube is provided in the bottom of the bag, and in the latter a blower located at the bottom of a vented bag is coupled to a transfer chute containing an air inlet, for the removal of solids from the bags. Whereas it has been recognized that gas assist means for the removal of solids from the bags may be helpful, presently known devices are expensive, complex, and less effective than desired. There exists a pressing need for fabric bags which can be more rapidly emptied of particulate solids, particularly fabric bags with bottom openings through which the solids can be more rapidly discharged without any necessity for destruction of the bags.